Ignorant parents are people who are unaware of how their behavior affects their own children.

First, parenting is behavior that is suited to train children into capable people, discipline them so they know how to navigate society, and help them grow into successful human beings. This can be done in many ways including having a mutually respectful relationship with children, helping them cultivate common sense and critical thinking to see why common sense makes sense, and helping them build their own problem-solving skills.
Ignorant parents are not knowledgeable about how to parent ethically.
Again, there are many ways to raise children, but the best results usually come from smart parenting.
Children who receive smart parenting feel good about themselves and their families, they are confident about their own decisions and they know that their parents did their best.
Ignorant parenting can leave children in the dust of their peers and eventually, under dirt.

AT A RESTAURANT
Jacob: why is Johnny cursing out the waiter? What a dick!
Gussac: oh, that's because his dad curses out waiters whenever he doesn't get what he wants. He told Johnny that waiters are inhuman and that they should be yelled at.
Jacob: ... like father like son, I guess.
Gassac: Yes. They both are huge dicks.

ON THE PHONE WITH A FRIEND
Hepa: My mom doesn't want me to attend a free communication workshop to work on good conversation techniques. I really want to be a fluent conversationalist.
Crystal: What!? That's an important skill to have! Is she nuts?
Hepa: No... she might not realize how important it is for my future career.
Crystal: An ignorant parent?
Hepa: Not sure...